1. Field of the Invention
The present in invention relates to ink jet recording apparatuses such as an ink jet printer.
2. Description of Related Art
Conventional ink jet printers include a thermal jet type and a piezoelectric material type. With the thermal jet type printer, an ink pressure chamber is provided with a heater which generates bubbles in accordance with print data. The bubbles expel ink drops through orifices, thereby performing a printing operation.
With the piezoelectric material type printer, electrical signals drive the piezoelectric material to deform, thereby creating internal pressures in the ink pressure chambers. The internal pressure expels the ink drops through orifices to perform a printing operation.
Ink jet printers for a color printing mode are provided with a plurality of groups of orifices, each of the groups corresponding to one of the primary color, i.e., yellow ink, magenta ink, cyan ink, and black ink.
Some printers are equipped with a printhead for black, the printhead having a larger number of orifices than printheads for primary colors so that a single scanning of the printhead in the main scanning direction (perpendicular to a direction in which the print medium travels) allows printing of two consecutive lines. This configuration permits high speed black printing.
Since color printing is performed less frequently than the monochrome printing, the printheads for the primary colors have a lesser number of orifices than does the printhead for black, thereby maintaining the cost of the color printer as low as possible.
Referring to FIG. 25, a printhead 11 includes four orifice plates 13-16. The orifice plates 13 and 14 are for a black head 11B. The orifice plates 15 and 16 are for yellow head 11Y, magenta head 11M, and cyan head 11C. The yellow head 11Y is at a leading end of the main scanning direction (illustrated at the upper side of FIG. 25) and the cyan head 11C is at a trailing end (illustrated at the lower side of FIG. 25). The magenta head 11M is between the yellow head 11Y and the cyan head 11C.
Each of the orifice plates 13 and 14 is formed with 54 orifices 12B at intervals of P1=0.169 mm such that orifices in one of the two plates are between those in the other plate. In other words, the orifices in the orifice plates 13 and 14 are staggered by P2=Pxc2xd (about 0.085 mm). Thus, the black head 11B has 108 orifices 12B which in effect provide a resolution or density of 300 DPI (Dots Per Inch).
Each of the orifice plates 15 and 16 is formed with 16 orifices 12Y for yellow ink at intervals of P1=0.169 mm such that orifices in one of the two plates are between those in the other plate. Thus, the yellow head 11Y has 32 orifices 12Y which effectively provide a resolution of 300 DPI (Dots Per Inch). Likewise, the orifice plates 15 and 16 are formed with orifices 12M and 12C arranged in the same manner as the orifices 12Y, so that magenta head and cyan head also provide a resolution of 300 DPI, respectively.
A total of 54 orifices 12B arranged at intervals of 0.169 mm covers approximately 9 mm(=0.169 mmxc3x9754). Therefore, if one line has a width of ⅙ in., driving the black head 11B to scan one time in the main scanning direction allows printing of two lines. Thus, the black printing can be fast.
The yellow head 11Y, magenta head 11M, and cyan head 11C each have as many orifices as about one-third the black head 11B. Accordingly, the color printing is performed at a speed that is about one-third the speed of the black printing.
An object of the invention is to provide an ink jet printer which can perform high speed printing without having to increase the manufacturing cost of the printer.
An ink jet recording apparatus comprises a black head and a plurality of color heads.
The black head has a predetermined number of first orifices aligned at predetermined intervals (e.g. 0.169 mm) in a sub-scanning direction (direction in which a print medium travels).
The plurality of color heads eject different colored ink drops. Each color head has the predetermined number of second orifices aligned in a direction parallel to the sub-scanning direction. All of the second orifices are aligned in directions parallel with a main scanning direction. The main scanning direction is perpendicular to the sub-scanning direction.
A black printing may be performed in a composite-black mode where a predetermined number of the color heads eject different colored ink drops to print one color dot one over the other to form a composite-black dot on a print medium. The composite-black mode prevents missing dots from the printer output resulting from ink exhaustion in the middle of the printing operation.
Black printing may be performed in an ink save mode where the black head ejects a black ink drop to form a black dot and at least one of the color heads ejects a corresponding colored ink drop to form a colored dot, so that the black dot and the colored dot are present on the print medium. The ink save mode prevents the missing dots from the printer output data resulting from the fact that ink runs dry in the middle of the printing operation.
A black printing may be performed in the composite-black mode while also using the black head. The black head ejects a black ink drop to form a single-black dot and the color heads eject corresponding colored ink drop to form a composite-black dot, the single-black dot and the composite-black dot being of different sizes.
A black printing may be performed in a high resolution mode using only black ink. The black head is moved in the second direction while ejecting ink drops onto the print medium in accordance with print data. Subsequently, one of the black head and the print medium is moved with respect the other such that the black head is displaced a distance substantially equal to a half the predetermined interval in the first direction. Finally, the black head is moved in a third direction opposite to the second direction while ejecting ink drops onto the print medium in accordance with the print data. The high resolution mode provide high resolution print quality with reduced printing speed.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.